| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package org.apache.gearpump.streaming.source |
| |
| import java.time.Instant |
| |
| import org.apache.gearpump.streaming.task.TaskContext |
| import org.apache.gearpump.Message |
| |
| /** |
| * Interface to implement custom source where data is read into the system. |
| * a DataSource could be a message queue like kafka or simply data generation source. |
| * |
| * An example would be like |
| * {{{ |
| * GenMsgSource extends DataSource { |
| * |
| * def open(context: TaskContext, startTime: TimeStamp): Unit = {} |
| * |
| * def read(context: TaskContext): Message = { |
| * Message("message") |
| * } |
| * |
| * def close(): Unit = {} |
| * } |
| * }}} |
| * |
| * subclass is required to be serializable |
| */ |
| trait DataSource extends java.io.Serializable { |
| |
| |
| /** |
| * Opens connection to data source |
| * invoked in onStart() method of [[org.apache.gearpump.streaming.source.DataSourceTask]] |
| * |
| * @param context is the task context at runtime |
| * @param startTime is the start time of system |
| */ |
| def open(context: TaskContext, startTime: Instant): Unit |
| |
| /** |
| * Reads next message from data source and |
| * returns null if no message is available |
| * |
| * @return a [[org.apache.gearpump.Message]] or null |
| */ |
| def read(): Message |
| |
| /** |
| * Closes connection to data source. |
| * invoked in onStop() method of [[org.apache.gearpump.streaming.source.DataSourceTask]] |
| */ |
| def close(): Unit |
| |
| /** |
| * Returns a watermark |
| * no timestamp earlier than the watermark |
| * should enter the system |
| */ |
| def getWatermark: Instant |
| } |